1. Field of the Invention
This invention relates to pipe restraining members and is directed more particularly to a collar member comprising at least one part of a pipe restraining assembly.
2. Description of the Prior Art
The provision of restraining assemblies suitable for retaining adjacent ends of pipes in a fixed position relative to each other is well known.
In U.S. Pat. No. 3,252,192, issued May 24, 1966, in the name of Joseph B. Smith, there is disclosed a pipe restraining assembly including two collar assemblies, one of which is installed proximate an end of one of the pipes. Each collar assembly includes two collar members which are provided with flanges adapted to be bolted together to form a pipe encircling collar assembly. Each of the two collar assemblies is provided with lugs which receive tie bolts to connect the collar assemblies to each other. Internally of the collar members are gripping surfaces adapted to engage the external surfaces of the pipes. To enhance pipe-gripping capability, the collar member gripping surfaces of Smith are provided with a layer of particles which are adapted to embed in the external surfaces of the pipes.
Examples of other restraining assemblies having collar members with gripping surfaces include U.S. Pat. No. 4,372,587, issued Feb. 8, 1983, in the name of Charles W. Roche, and U.S. Pat. No. 4,568,112, issued Feb. 4, 1986, in the name of Earl C. Bradley et al., in which serrations are used to engage and grip the pipe members.
It is common practice in the pipe jointing industry to dimension the internal radius of collar members substantially equal to the external radius of the pipe to which the collar members are to be applied. When protrusions are placed on the internal surface of the collar member, such protrusions extend inwardly of the radius of the collar member and therefore inwardly of the radius of the pipe. Such practice has been believed to insure intimate contact between the collar member internally extending protrusions and the pipe exterior. However, when a collar member is so configured, it often results in the protrusions nearest the flange portions at the ends of the collar member being forced over the pipe during installation, with the protrusions scraping along and biting into the exterior of the pipe until they come to their final position. Inasmuch as the collar member usually is formed of a relatively massive and unyielding band of metal, to insure longevity in service, the collar member has little resiliency to aid in installation, that is, in slipping over the pipe when there are interfering internal projections on the collar member.
It has been found that in the use of protrusions, including teeth, prongs, or the like, the protrusions nearest the ends of the collar member generally bite substantially deeper into the pipe than do the protrusions at or near the center of the collar member. In extreme instances, the end protrusions have been found to bite deeply into the pipe, while the center protrusions fail to touch the pipe. Accordingly, it would be beneficial if protrusions on the gripping surfaces of restraining collar members were configured and dimensioned such that contact and engagement with the pipe retained thereby were more nearly uniform.